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METS  December 2001

METS December 2001

Subject:

Notes comparing LC and MSU audio tech MD

From:

Carl Fleischhauer <[log in to unmask]>

Reply-To:

Metadata Encoding and Transmission Standard <[log in to unmask]>

Date:

Tue, 4 Dec 2001 09:43:35 -0500

Content-Type:

TEXT/PLAIN

Parts/Attachments:

Parts/Attachments

TEXT/PLAIN (111 lines)

This is a second message from the Carl-struggles-with-metadata
story.  This one is REALLY deep in the weeds of audio.  Michigan State,
Harvard, and our LC team wish fervently to come up with a common shared
tech extension schema for audio (next: images and video and even
text!)   This email is framed as a dialog with MSU since they have a new
layout that took our layout as a starting point.  The MSU web page for
schemas is http://matrix.msu.edu/ngsw/schema.cfm.  But although this is a
bit of a dialog, I thought that other METS folks may have an interest and
(in fact) may know more than we do and thus will shed some light in dark
corners.

MSU element 8:  channels (e.g. mono)

LC response: Inspired by Dave Ackerman at Harvard, we use three
elements/attributes for this ("fields" in our relational database).  We
are playing it safe in the digital realm but also trying for an
all-purpose set to serve both digital files and analog source items:
- channel_track_quantity (how many channels/tracks?)
- channel_track_info (what is on each channel, e.g., for a multitrack
item: left is French, right is English)
- sound_field (this is for what amount to the
"expressive" dimension: "stereo," "joint stereo," "mono," "surround," and
whatever we call our multi-channel, multilingual example: "separate
parallel streams" or something)
At this moment, I prefer the "discrimination" that our three-part approach
offers.

MSU element 4: bitrate

LC response: We have two fields for this: data_rate and
data_rate_mode.  The former provides the rate or the AVERAGE rate (for
variable bit rate) and the mode unit is where we say "fixed" or
"variable."  At the moment, we don't intend to produce variable bit rate
audio (we might in future) but we are very likely to acquire some.  And we
want to parallel this element/attribute set in the video realm, where it
is MORE LIKELY that we will produce or receive variable bit rate
compressed-video examples.  Thus we continue to prefer the two-part
approach.

MSU element 6: filetype, (e.g. Microsoft RIFF Wave)

LC response: I am not sure that I understand this properly.  Let me put it
this way, what exactly is added here that is not expressed by
internet_media_type (AKA MIME_type)?

Your short and long definitions make much of a corporate name, e.g.,
Microsoft.  Does this do more than identify the source of the format, in
which case once you know the format's MIMEtype, then you can learn the
source and get at documentation by "class" methods? [This is a TIFF
file.  TIFF comes from Aldus/Adobe.  This file is in my repository's TIFF
class and I go to the "class information" to get the details and
documentation.]

Your long definition mentions ".raw" files (new to me, maybe something
that an Apple Macintosh does and I don't know about it).  But if so, I
would argue for inventing a MIMEtype(s) for "raw" (or various types of
"raw"), and treating it/them as an internet_media_type.

Help me out -- what have I missed here?

MSU element 7:  fileformat (e.g. PCM)

LC response: This one is really a puzzler to us.  It seems to be about
structural stuff inside a file: your examples include PCM (the sampling
"type") and byte order (big and little endian).  Then there is mention of
stuff I never heard of: Lernout and Hauspie SBC 16kbs, CCITT u-Law.

Are these DIFFERENT facts about a file that we need to be able to
parse?  If so, I worry about lumping them in a single field, UNLESS the
set of facts always maps in the same way to a given type of file, or
UNLESS they can more easily be auto-extracted as a set.

I know that byte_order can make a difference for images ("Intel
TIFF" vs. "Motorola TIFF") and some software (rarely) has trouble reading
one or the other type.  Thus there may be a parse-able argument for byte
order.  Perhaps the same is true of PCM.  The only alternate sampling
structure that I know about is SONY's DSD (for their audio DVD) and LC may
acquire some content in this form in the future.  But this seems to me to
argue for a separate parseable field/element/attribute.

You'll have to help me by explaining what to make of Lernout and Hauspie
SBC 16kbs, CCITT u-Law.

But I will ask about one similar unit that we have and you did not pick
up: compression_codec, AKA compression_method.  This, we thought, would
NOT need to be parseable.  Any MP3 or MPEG-video player, for example, is
likely to play any conforming file.  But the QUALITY of the file may
reflect what codec was used to make it.  Frauenhofer is thought to be
better than something-or-other.  In the video realm, Sorenson Quicktime is
thought to be better that Cinepak.  So we thought to keep this unit of
information to answer the future question, "why does this one sound/look
so awful?"  This data may end up also being captured in DIGIPROVMD but for
now we are inclined to keep it in TECHMD.

Now, are there other things like codec that may be interesting but do not
need to be parseable?  Perhaps there is a catchall element/attribute
here?  Dave Ackerman at Harvard had something he called
"format_specification" (which might blow up to format_specification_name
and format_specification_info) that he thought of as a repeating
field.  Maybe there is some merit to a catchall category?

Conclusion: we drift toward having a threesome:
- byte_order
- sampling_type (??)
- compression_codec OR format_specification_name and
format_specification_info

Whew!  Discussion welcome!!  I am trying to learn!!!

Best from Carl

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